Metal Mold Research Articles

Rapid Two-Stage Norwood Procedure Using an Auto-Pericardial Patch Fixed with an Arch-Shaped Mold

While the classical 1-stage Norwood procedure is still performed, there are several types of “hybrid” procedures for the management of hypoplastic left heart syndrome. These hybrid approaches consist of bilateral pulmonary artery banding with ductal stenting or prostaglandin infusion as the first-stage palliation, followed by a second-stage Norwood procedure or comprehensive stage II procedure. Since 2012, we have adopted a rapid 2-stage Norwood procedure as a routine strategy, where bilateral pulmonary artery banding is performed within 5 days of age with balloon atrial septectomy, if needed, before the development of hemodynamic instability. The second-stage Norwood procedure is performed within 1 month of age. The arterial duct is kept open by continuing prostaglandin administration. In addition, an important improvement of our Norwood procedure is the use of an auto-pericardial patch fixed on an arch-shaped metal mold. The pericardium is wrapped around the lesser curvature of the mold and treated with 0.6% glutaraldehyde for 15 min. This makes it easier to imagine the final shape of the arch and helps to enlarge the retroaortic space significantly, which could reduce the risk of bronchus or central pulmonary artery stenosis and facilitate hemostasis. These developments in strategy and procedure could improve our surgical results. While the classical 1-stage Norwood procedure is still performed, there are several types of “hybrid” procedures for the management of hypoplastic left heart syndrome. These hybrid approaches consist of bilateral pulmonary artery banding with ductal stenting or prostaglandin infusion as the first-stage palliation, followed by a second-stage Norwood procedure or comprehensive stage II procedure. Since 2012, we have adopted a rapid 2-stage Norwood procedure as a routine strategy, where bilateral pulmonary artery banding is performed within 5 days of age with balloon atrial septectomy, if needed, before the development of hemodynamic instability. The second-stage Norwood procedure is performed within 1 month of age. The arterial duct is kept open by continuing prostaglandin administration. In addition, an important improvement of our Norwood procedure is the use of an auto-pericardial patch fixed on an arch-shaped metal mold. The pericardium is wrapped around the lesser curvature of the mold and treated with 0.6% glutaraldehyde for 15 min. This makes it easier to imagine the final shape of the arch and helps to enlarge the retroaortic space significantly, which could reduce the risk of bronchus or central pulmonary artery stenosis and facilitate hemostasis. These developments in strategy and procedure could improve our surgical results.

Effect of Mg on the fluidity of zinc alloys

A good fluidity is an important condition for the casting and molding of zinc alloys, but there is no systematic study on the effect of Mg on the fluidity of zinc alloys. The effect of Mg on the fluidity of pure zinc or Zn-Mg alloy liquid was studied by spiral mobility stainless steel metal mold, DSC, and optical microscopy under the conditions of metal typecasting. The results show that the addition of Mg into pure zinc decreases the fluidity of pure zinc liquid, while the fluidity of Zn-Mg alloy liquid improves as the Mg content rises near the eutectic point, but is still lower than that of pure zinc. Zinc dendrites formed in zinc alloy liquid after the addition of Mg is the main reason for the deterioration of the fluidity.

Life Cycle Assessment of Metal Products Produced by Additive Manufacturing: A Metal Mold Case Study

Additive manufacturing represents a promising technology with strong potential for future applications, which is ever widening due to the progressive removal of technological and economic barriers. This study is directed at quantifying the environmental and economic benefits, across the entire life cycle, of the application of additive technology direct metal laser sintering (DMLS) in the production of metal molds in comparison with their conventional production. The molds produced by the technologies under comparison are designed for die casting of zinc parts for the automotive industry. An important part of this article is an overview and comparison of available life cycle analysis studies focused on the additive manufacturing of metals. The results of this study demonstrate that although the material used in 3D printing brings higher environmental impacts and is significantly more expensive, even in the production phase additive technology is associated with lower impacts in most categories evaluated by the chosen method of IMPACT 2002+. Even greater benefits are associated with the use phase. Similar results are achieved in the evaluation of levels of cumulative energy demand, greenhouse emissions, and life cycle costs.

Graphite Compactness Degree and Nodularity of High-Si Ductile Iron Produced via Permanent Mold versus Sand Mold Casting

In recent years, high-Si ductile cast irons (3–6% Si) have begun to be used more and more in the automotive and maritime industries, but also in wind energy technology and mechanical engineering. Si-alloyed ferrite has high strength, hardness and oxidation and corrosion resistance, but it has low ductility, toughness and thermal conductivity, with graphite as an important influencing factor. In this study, 4.5% Si uninoculated ductile iron solidified in thin wall castings (up to 15 mm section size) via a permanent (metal) mold versus a sand mold, was evaluated. Solidification in a metal mold led to small size, higher graphite particles (less dependent on the section size). The graphite particles’ real perimeter was 3–5% higher than the convex perimeter, while the values of these parameters were 41–43% higher in the sand mold. Increasing the casting section size led to an increased graphite perimeter, with it being much higher for sand mold. The graphite particles’ shape factors, involving the maximum and minimum size, were at a lower level for metal mold solidification, while by involving the difference between Pr and Pc, is higher for the metal mold. The shape factor, including the graphite area and maximum size, had higher values in the metal mold, sustaining a higher compactness degree of graphite particles and a higher nodularity regarding metal mold solidification (75.5% versus 67.4%). The higher was due to the graphite compactness degree level (shape factor increasing from 0.50 up to 0.80), while the lower was due to the graphite nodularity for both the metal mold (39.1% versus 88.5%) and the sand mold (32.3% versus 83.1%). The difference between the metal mold and sand mold as the average graphite nodularity increased favored the metal mold.

Effect of Varying Percentage Increase in Reinforcement on Some Mechanical Properties of Die Cast Aluminum Alloy Composites

The die-casting process is a metal casting processes that utilize metal molds or permanent dies. In this work, the effect of varying percentage increase in reinforcement on some mechanical properties of aluminum alloy composites was obtained by the die cast process. The process was applied to produce various casts using aluminum alloy as the metal matrix and sawdust as the reinforcement at 5%, 10% and 15% by weight. Aluminum Scrap was sourced and sent for elemental characterization at Engineering Materials Development Institute (EMDI), Akure Nigeria. Tensile and hardness test were the mechanical tests carried out on the different samples of the cast. The elemental characterization test result showed that, the composition of the aluminum alloy used is Al-8.1%Mg-0.4%Fe-0.2%Zn. Results showed that at 10% by weight of reinforcement, the average tensile strength of the composite had the highest value while the lowest tensile strength was recorded at 15% by weight of reinforcement. At 15% by weight of reinforcement, the average hardness of the composite had the highest value while the lowest hardness was recorded at 5% by weight of reinforcement. Results were compared with the works of Ranjit et al. (2020) and Belete et al. (2013) and it was concluded that the results obtained from this work are adequate and significant for use.

The Effect of Carbonated, Isotonic, and Yoghurt Drinks to the Hardness of Bulk Fill Composite Resin

Background: Composite resin often used as a restoration material due to its advantages in the aesthetic field. The bulk-fill type is one of the composite resin that can be applied directly into cavities as deep as 4 mm, so that restoration procedure becomes easy and effective. Hence, exposure to various acidic drinks can reduce the hardness of composite resins and eventually lead to failure of the tooth restoration process.Objective: This research aimed to evaluate the effects of several commercial acidic drinks, (carbonated, isotonic, and yogurt) on the hardness of bulk-fill composite resins.Method: This research was an experimental study with a post-test control group design. Twenty-four specimens were made with the size 10 x 4 mm using the metal mold rings. Specimens were divided into 4 groups for artificial saliva (served as a control), carbonated, isotonic, and yogurt. Specimens were immersed in storage agents for 5 seconds followed by artificial saliva for 5 seconds. This cycle was repeated 20 times for 14 days. The bulk-fill composite resin hardness was measured using a Micro Vickers Hardness Tester with a load of 100 grams for 10 seconds. Statistical analysis was performed using One Way ANOVA and Post Hoc LSDResults: Data were normally distributed and homogeneous with p > 0.05. The One Way ANOVA test showed the biggest difference in bulk fill composite resin between 4 groups (p < 0.001). The Post Hoc LSD test showed significant differences between all groups (p < 0.001)Conclusion: Carbonated, isotonic, and yogurt drink significantly decreased surface microhardness of bulk-fill composites resin but the carbonated drinks greatly reduce the hardness value since it has the lowest pH of 2.3.

Comparative analysis of flexural strength of four commercially available dental restorative materials

Background: The objective of this in vitro study was to investigate the flexural strengths of four commercially available restorative materials. The restorative materials used in this study were - Posterior Glass ionomer cement (GC Fuji), Resin modified Glass ionomer cement (GC), Ketac molar (3M ESPE), Miracle mix (XP). Materials and Methods :- Four restorative material under study were divided into 4 groups with each group containing five specimens of 2 mm × 2 mm × 25 mm of restorative material prepared according to ISO 9917-2 standard using a customized metal mould. After light polymerization, the specimens were stored in distilled water at 37°C for 24 hours. The specimens were subsequently blotted dry, measured and subjected to flexural testing using an Instron universal testing machine (Tinius Olsen) at a crosshead speed of 1mm/min until the specimen fractured. Results: - Data collected was statistically analysed using Kruskal Walli’s Test and Chi Square test. The result showed that the mean flexural strength of Ketac Molar> Miracle Mix > RMGIC > Posterior GIC. Conclusion: -The knowledge of mechanical properties of the various materials is important for the long-term clinical success of material.

Flexible metallic mold based precision compression molding for replication of micro-optical components onto non-planar surfaces

Replication of micro/nano-scale optical components onto non-planar substrates is considered technically challenging and excessively expensive via existing manufacturing approaches. A low-cost, large-volume and high-precision fabrication approach is thus highly desirable. In this paper, a novel precision compression molding approach that enables large-volume and high-resolution replication of micro/nano-scale optical features from planar to non-planar substrates is proposed. A micro-lens array is demonstrated to be transferred from a planar master mold to a non-planar substrate. In such process, a micro-lens array mold is initially fabricated by single-point diamond turning on a planar mold surface and then replicated by micro-injection molding. After that, the optical structures are transferred from micro-injected polymeric samples to a nickel foil by electro-plating, which is employed as a critical transition medium. To obtain sufficient flexibility with considerable strength, the thickness of the electro-plating mold is controlled to be around 75 μm, which is further integrated with precision molding tools to replicate micro/nano-scale optical features onto cylindrical substrates. Geometrical profile and surface roughness of the fabricated optical components in each processing step are characterized experimentally. The results indicate that the replication of the micro-lens array successfully demonstrates the process to transfer micro-optical components from planar surfaces to non-planar thermo-plastic polymeric substrates with high fidelity and optical-level surface quality. Compared with conventional precision compression molding, this novel proposed method in this research could achieve much higher flexibility and comparable fidelity with low cost on transferring optical structures from planar to non-planar surfaces. The application of this method might be widely extended to numerous replication methods, such as precision glass molding, roll-to-roll and roll-to-plane imprinting.

Evaluation of Microhardness of Two Bulk-fill Composite Resins Compared to a Conventional Composite Resin on surface and in Different Depths.

Statement of the Problem: One of the problems with light-cured composite resins is the limitation and inadequate depth of curing and polymerization, resulting in low surface microhardness and restoration failure.Purpose: The present study aimed to compare the surface microhardness of two different bulk-fill composite resins and one conventional composite resin using the Vickers microhardness test.Materials and Method: In the present in vitro study, 108 samples from two different bulk-fill composite resins (Tetric N Ceram and Xtrafil) and one conventional composite resin (Filtek Z250) were prepared in metallic molds (2×4×10 mm) (n=36 for each composite resin). Six samples from each composite resin (n=6) underwent a hardness measurement test at specific depths (0.1, 1, 2, 3, 4 and 5mm). The samples were then stored at 37ºC for 24 hours, followed by a microhardness test at the depths mentioned above.Results: In all the composite resin samples, microhardness decreased with an increase in depth. The highest microhardness was recorded in Filtek Z250, followed by Xtrafil, with no significant difference. The lowest microhardness was recorded in Tetric N Ceram bulk-fill. Both bulk-fill composite resins at all the depths exhibited depth-to-surface standard microhardness (>80%).Conclusion: According to the results, both evaluated bulk-fill composite resins exhibited favorable surface microhardness up to a depth of 5 mm.

Energy absorption in carbon fiber honeycomb structures manufactured using a liquid thermoplastic resin

In this study, carbon fiber/thermoplastic (Elium®) honeycombs were manufactured using the resin infusion process in a customized metallic mold. Honeycomb cores, based on different carbon fiber layers, were manufactured to achieve four different fiber weight fraction composites. Two different types of specimens, based on a single honeycomb cell and five honeycomb cells, were prepared and subjected to compression loading. The results of these tests were compared with data from similar honeycomb structures based on carbon fiber–reinforced epoxy composite. It has been shown that the compressive strength and the specific energy absorption capacity of the honeycombs increase rapidly with increasing fiber weight fraction. The specific energy absorption capability of the novel thermoplastic honeycomb structures has been shown to be as high as 50 kJ/kg which compares favorably with other energy-absorbing core materials. The thermoplastic honeycomb specimens exhibited a similar specific energy absorption capability and an improved compressive strength compared to their epoxy counterparts. Furthermore, the CF/thermoplastic honeycombs exhibited enhanced structural stability and displayed a more uniform and progressive core failure mode than the longitudinal splitting observed in the CF/epoxy honeycombs. The honeycomb core that exhibited the best performance was then used to manufacture thermoplastic sandwich specimens based on CF/thermoplastic face sheets. Three point bend tests were conducted to determine the flexural strength of the sandwich samples and to identify the failure modes. Optical micrographs revealed that the flexural damage was primarily due to the core crushing and adhesive failure between the core and the composite skins.

Development of a Novel Transcription Molding Process to Fabricate Sophisticated Polymer Products with Precise Microstructure and High Transparency Applicable to Display Devices and Bio-chips

Abstract In this study, we developed a novel transcription-molding process and experimentally discussed its validity for fabricating polymer products having the precise microstructure on the surface. The process was named “Melt-Transcription Process” which consists of two characteristic stages; coating and compression. In the coating stage, a molten polymer is coated on the surface of a metal mold having the precise microstructure by a coating device specially designed in this study. The thickness of the coated polymer melt is typically 100 μm or more. Immediately after coating, the coated polymer is compressed against the mold surface so as to make the polymer flow into the microstructure cavities engraved on the mold, and to fabricate the 3-dimensional structure of polymer products. The pressure required for compression is quite lower than that in conventional nano-imprinting process, because the molten polymer of high temperature is distributed in advance over the mold surface in the coating stage. The “Melt-Transcription Process” was applied to fabricate polymer products with the size of 150 mm in length, 150 mm in width and 1 mm in thickness, having the microstructure of tens micrometers on their surface. Cyclo-olefin polymer (COP) and Polymethyl methacrylate (PMMA) were used as the polymer materials, and the dimensions and transcription ratios (the ratio of the height of the transcribed microstructure to the depth of the microstructure on the mold) of the molded microstructure were experimentally evaluated. As a result, by the Melt-Transcription Process, the microstructure was sufficiently transcribed on a very thin substrate of large surface area with high transcription ratios, typically 95% or more, under relatively low compression pressure of less than 10 MPa. The process was also applied for fabricating products with a range of thicknesses and we could experimentally verify that products composed of a membrane of 80 μm thickness and a surrounding frame with 1.95 mm thickness were successfully molded. Furthermore, we fabricated a micro-lens array product by using film grade PMMA with relatively higher viscosity in a product having 125 μm in thickness and a size of 102 mm × 102 mm.

Toward a Better Understanding of Shock Imprinting with Polymer Molds Using a Combination of Numerical Analysis and Experimental Research.

In the last decade, a new technique has been developed for the nanoimprinting of thin-metal foils using laser-induced shock waves. Recent studies have proposed replacing metal or silicone molds with inexpensive polymer molds for nanoimprinting. In addition, explosive-derived shock waves provide deeper imprinting than molds, greatly simplifying the application of this technology for mass production. In this study, we focused on explosive-derived shock waves, which persist longer than laser-induced shock waves. A numerical analysis and a set of simplified molding experiments were conducted to identify the cause of the deep imprint. Our numerical analysis has accurately simulated the pressure history and deformation behavior of the workpiece and the mold. Whereas a high pressure immediately deforms the polymer mold, a sustained pressure gradually increases the molding depth of the workpiece. Therefore, the duration of the pressure can be one of the conditions to control the impact imprint phenomenon.

Effect of Ce on the Microstructure and Corrosion Resistance of Al-5Mg-3Zn-1Cu Alloy

The effects of different Ce content on the microstructure and corrosion resistance of Al-5Mg-3Zn-1Cu alloy in metal mold gravity casting were studied in this paper. The microstructure of the alloy was characterized by scanning electron microscope (SEM) and X-Ray diffractometer (XRD). The corrosivity of all alloys in 3.5 wt.%NaCl solution was studied by electrochemical and immersion corrosion techniques. The results show that the microstructure of the alloy is mainly composed of α-Al, T phase, and Al2Cu phase. Ce can refine the organization of the alloy, but when the addition of Ce is higher than 0.25 wt.%, a massive Ce-rich phase appears in the alloy. The results of a potential polarization test show that the corrosion potential of the alloy increases obviously from −1.253 V to −1.193 V with the increase in Ce content in the alloy.

Development of High-Sensitivity Electrically Conductive Composite Elements by Press Molding of Polymer and Carbon Nanofibers.

Carbon nanofibers (CNFs) have various excellent properties, such as high tensile strength, electric conductivity and current density resistance, and thus have great application potential in electrical sensor development. In this research, electrically conductive composite elements using CNFs sandwiched by thermoplastic olefin (TPO) substrates were developed by press molding. The metal mold used for press molding was processed by a femtosecond laser to generate laser-induced periodic surface structures (LIPSS) on the mold surface. The aggregate of CNFs was then flexibly fixed by the LIPSSs imprinted on the TPO substrate surface to produce a wavy conductive path of CNFs. The developed composite elements exhibited a sharp increase in electrical resistance as strain increased. A high gauge factor of over 47 was achieved, which demonstrates high sensitivity against strain when the composite element is used as a strain gauge. Scanning electron microscope observation revealed that the TPO filled the spaces in the aggregate of CNFs after press molding, and the conductive path was extended by the tensile strain. The strain-induced dynamic changes of contact states of CNFs and CNFs networks are discussed based on the electrical performance measurement and cross-sectional observation of the elements. This research provides a new approach to the production of flexible and high sensitivity strain sensors.

Modelling of metal – mould interface resistance in the Al-11.5 wt.% Si alloy casting process

AbstractA computational model is developed to include heat transfer, effects of resistance of the metal –mould interface, and pressure in the simulation of the solidification process. The simulation of the interface resistance is based on the Zero Thickness Element, utilizing the Finite Element Method. The solid boundary conditions, including contact resistances, have been modified by a pressure gradient in each of the Zero Thickness Elements. The pressure gradient has been modelled on experimental data. In order to verify the computational results, an Al-11.5 wt.% Si alloy has been poured into a permanent mould and the temperature of the interface measured. Then we modelled the effect of metallostatic pressure on the overall heat transfer coefficient in the metal–mould interface. The comparison between the experimental and the simulation results during the solidification process shows a good consistency that confirms the accuracy of the model for the effect of the interface resistance on solidification time.

Marginal microleakage and modified microtensile bond strength of Activa Bioactive, in comparison with conventional restorative materials.

This study aimed to assess the enamel and dentin marginal microleakage and dentin microtensile bond strength (μTBS) of ACTIVA BioACTIVE Restorative with and without a bonding agent compared with conventional restorative materials. For enamel and dentin microleakage, Class II boxes were prepared in the mesial (1 mm under the cementoenamel junction) and distal (1 mm above the cementoenamel junction) surfaces of 90 extracted human third molars. The teeth were randomly divided into five groups (n = 18): Group Z (G-Premio Bond + Filtek Z250 XT), Group X (G-Premio Bond + X-tra fil bulk-fill), Group AA (G-Premio Bond + Activa Bioactive restorative), Group A (Activa Bioactive restorative), and Group G (dentin conditioner + Fuji II LC Improve). The teeth were thermocycled, and their microleakage was quantified using the dye penetration test under a stereomicroscope. For dentin μTBS measurement, 12 specimens were fabricated in metal molds (1 × 1 × 12 mm³) for each group mentioned above, and a universal testing machine measured their μTBS. Data were analyzed using one-way analysis of variance (ANOVA), the Kruskal-Wallis test, and multiple comparisons tests. Significant differences were noted among the groups in marginal microleakage and μTBS (p < .001). The highest mean microleakage scores at the enamel and dentin margins were noted in Group A, which had significant differences with other groups (p < .001). The highest μTBS was found in Group X, with significant differences with Group G and Group A (p < .05). The lowest µTBS was noted in Group A, with significant differences with Groups X, Group AA, and Group Z (p < .001). Activa Bioactive without a bonding agent showed significantly lower µTBS to dentin, and higher microleakage at the enamel and dentin margins. Application of adhesive resin with Activa Bioactive provided a dentine bond strength and marginal seal comparable to other restorative materials.

Fluorinated Ethylene Propylene Coatings Deposited by a Spray Process: Mechanical Properties, Scratch and Wear Behavior

To increase the lifetime of metallic molds and protect their surface from wear, a fluorinated ethylene propylene (FEP) polymer was coated onto a stainless-steel (SS304) substrate, using an air spray process followed by a heat treatment. The microstructural properties of the coating were studied using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) as well as X-ray diffraction. The mechanical properties and adhesion behavior were analyzed via a nanoindentation test and progressive scratching. According to the results, the FEP coating had a smooth and dense microstructure. The mechanical properties of the coatings, i.e., the hardness and Young’s modulus, were 57 ± 2.35 and 1.56 ± 0.07 GPa, respectively. During scratching, successive delamination stages (initiation, expansion, and propagation) were noticed, and the measured critical loads LC1 (3.36 N), LC2 (6.2 N), and LC3 (7.6 N) indicated a high adhesion of the FEP coating to SS304. The detailed wear behavior and related damage mechanisms of the FEP coating were investigated employing a multi-pass scratch test and SEM in various sliding conditions. It was found that the wear volume increased with an increase in applied load and sliding velocity. Moreover, the FEP coating revealed a low friction coefficient (around 0.13) and a low wear coefficient (3.1 × 10−4 mm3 N m−1). The investigation of the damage mechanisms of the FEP coating showed a viscoelastic plastic deformation related to FEP ductility. Finally, the coating’s resistance to corrosion was examined using electrochemical measurements in a 3.5 wt% NaCl solution. The coating was found to provide satisfactory corrosion protection to the SS304 substrate, as no corrosion was observed after 60 days of immersion.

Compressive Strength Determination of Granite Dust-Sandcrete

This study entails the research data of the empirical study carried out on the compressive strength determination of Granite dust-Sandcrete with granite dust as partial replacement of three (3) grades of river sand with fineness modulus (fm) of 2.29, 2.44 and 2.89. The percentage replacements range from 0%, 10%, 20%, 30%, 40%, 50% to 100%. A gross number of 102 cubes of 150 × 150 × 150mm square metallic mould were blend, mixed and cast with a mix ratio of 1:5. Three (3) cubes were blend, mixed and cast for each percentage partial replacement and a total 34 cubes for each grade of river sand, were crushed to derive the compression strength of 28th day curing respectively. For river sand with fineness modulus of 2.29, the highest strength was recorded on 80% replacement, while the least strength was recorded on 0% replacement. For the same river sand, compressive strength increased from 0% to 80% and assumed a descending trend from 80% to 100%. For 2.44 fineness modulus, the highest strength was recorded on 80% replacement, while the least strength was recorded on 0% replacement. Also, for the same river sand, compressive strength increased from 0% to 80% and assumed a descending trend from 80% to 100%. For river sand of 2.89 fineness modulus, the highest strength was recorded on 70% replacement, while the least strength was recorded on 0% replacement. Also, compressive strength increased from 0% to 70% and assumed a descending trend from 70% to 100%. Generally, the compressive strength assumed an upward trend as the percentage replacement increases.

Influences of the workpiece material and the tool-surface engagement (TSE) on surface finishing when ball-end milling

This paper explains and quantifies the effects of the tool-surface engagement (TSE) on the workpiece finishing when using a ball-end tool in free-form milling of metallic mold materials with distinct elastoplastic responses. Electrolytic copper and AISI H13 steels were machined under different TSE and monitored for Sz roughness and cutting energy. As a result, two different cutting mechanisms named Tip-On and Tip-Out were identified. In Tip-On, the tooltip directly contributes to the part final surface formation, while at Tip-Out the tooltip only takes part of the chip removal without participating in the part surface generation. Accumulated cutting energy during every chip formation was also calculated based on machining force measured experimentally. With accumulated cutting energy 10 times lower than down-milling, the up-milling mode improved the part roughness by 43% at the Tip-Out mechanism. Contrary, down-milling produced four main surface damages due to the higher accumulated cutting energy, i.e., plastic deformation and side flow in ductile parts and cavities and scratches in harder workpieces. Real Sz roughness was 7 to 19 times higher than the theoretical one with major influences of the TSE and workpiece material. In conclusion, hand finishing can be reduced by applying up-milling and Tip-Out strategies when milling free-forms of harder workpieces.

Influence of surface roughness of die sinking EDM on mold releasability in compression molding of thermosetting phenol resin

Improvement in metal mold characteristics such as wear resistance, corrosion resistance and mold releasability is essential for plastic molding. In this study, factors of the mold releasability were investigated by quantitative evaluations of adhesion forces between the processed metal mold surfaces and the molded resins in compression molding of thermosetting phenol resin. Die sinking EDM was employed as the processed surfaces of the metal molds. As the mold releasability tests, the molded thermosetting phenol resin onto the EDMed surface was pulled up in the perpendicular direction from the surface. Consequently, the mold releasability could be quantitatively evaluated by measuring a maximum tensile load which means a mold release force when the molded resin is separated from the EDMed surface.Several workpieces with different surface roughness as the EDMed surfaces were prepared by varying discharge currents and pulse durations. As a result of investigations on relationships between surface roughness parameters and measured mold release forces, the mold release forces tended to increase as maximum height roughness RZ and average length RSm of the surface roughness parameters increase. On the other hand, the mold release forces tended to decrease as peak count RPc increases. Accordingly, it is considered that anchor effects become higher with increase of undulation on the EDMed surfaces. Therefore, the undulation is one of the factors affecting the mold releasability, and it would be possible to improve the mold releasability by reducing the undulations on the EDMed surfaces with EDM conditions.